Wavelength division multiplexing (WDM) has been explored as an approach for increasing the capacity of fiber optic networks to support the rapid growth in data and voice traffic applications. A WDM system employs plural optical signal channels, each channel being assigned a particular channel wavelength. In a WDM system, signal channels are generated, multiplexed, and transmitted over a single waveguide, and demultiplexed to individually route each channel wavelength to a designated receiver. Through the use of optical amplifiers, such as doped fiber amplifiers, plural optical channels are directly amplified simultaneously, facilitating the use of WDM systems in long-distance optical systems.
Proposed wavelength division multiplexed optical communication systems typically include multiplexer and demultiplexer switching elements which permit only a fixed number of optical channels to be used in the optical system. In one optical system configuration, for instance, the multiplexed signal is broken down into its constituent optical signals through the use of an integrated frequency router demultiplexer. The frequency router uses silicon optical bench technology in which plural phosphorus-doped silica waveguides are disposed on a silicon substrate. An optical star outputs to an array of N waveguides having adjacent optical path lengths which differ by q wavelengths; this array in turn feeds an output N×N star. Such a frequency router design for an optical communication system is described in Alexander et al., J. Lightwave Tech., Vol. 11, No. 5/6, May/June 1993, p. 714. Using a 1×N configuration at the input, a multiplexed optical signal containing light of different frequencies is separated into its component frequencies at each waveguide extending from the output N×N star. Although this configuration adequately separates light of different frequencies, the integrated optical design fixes both the number and the respective wavelengths of the optical channels. Additionally, each wavelength has a fixed relationship between a particular pair of input and output ports of the routing element.
The deployment and serviceability of the aforementioned switching elements becomes problematic as the number of channels, and hence the number of input and output ports, increases to support future DWDM networks, which may have anywhere from 256 to thousands of channels. Since each port is assigned a unique wavelength that cannot be changed, a field technician must ensure that the proper transmitter operating at the appropriate wavelength is connected to the proper port of the switching element. These connections are typically manually provisioned to the front bay of the switching element. Assuming fixed-wavelength transmitters are employed, the technician may be required to install thousands of different transmitters so that each transmitter is properly connected to its corresponding port. Accordingly, this installation procedure can be quite time consuming and prone to error, while also requiring that it be performed by a skilled technician.
Ideally, a so-called “plug and play” approach would be employed in which the technician connects any one of a series of transmitters to any of the ports of the switching element so that provisioning can be accomplished quickly and in a nearly error-free manner by a technician having minimal training.